1. Field of the Invention
The invention relates to a technology that generates images to be displayed on a display apparatus installed in a vehicle.
2. Description of the Background Art
A conventionally-known image display system is of a type for installation in a vehicle, such as a car, to display images of the surroundings of the vehicle shot with a camera mounted on the vehicle, on an in-vehicle display. By using the image display system, a driver can understand the situation around the vehicle in substantially real time.
For example, a region outside a front fender of the vehicle, which is an opposite side to a driver seat, is often a blind spot for a driver. Therefore, it is difficult for the driver to understand a clearance between the vehicle body and an obstacle. On the other hand, when the image display system is used, an on-vehicle camera shoots images showing the region outside the front fender and the images are displayed on an in-vehicle display. As a result, the driver can easily see the clearance between the obstacle and the vehicle body in the region on the opposite side of the driver's seat, for example, when closely approaching a roadside.
In a dark surrounding environment, such as at night, there is a case where the images of the surroundings of the vehicle cannot be displayed with enough brightness because light exposure is insufficient for such an image display system to shoot images. Therefore, it is proposed to illuminate the region to be shot with the camera, by providing auxiliary light from an auxiliary light source for assisting in shooting images when the surrounding environment is relatively dark.
Recently, a new image display system is proposed that generates a composite image, showing the surroundings of the vehicle viewed from a virtual viewpoint such as a point directly above the vehicle by using a plurality of images of the surroundings of the vehicle shot with on-vehicle cameras and that displays the composite image on a display. Such an image display system allows a relatively broad range of the surroundings of the vehicle to be displayed on a display.
Even when this image display system is used, it is preferable to illuminate a surrounding area of the vehicle in a dark surrounding environment, in accordance with the relatively broad region able to be displayed. Although a lighting system such as headlights and taillights used for driving can illuminate a part of the region able to be displayed, it is preferable that an auxiliary light source illuminates the region that the lighting system for driving cannot illuminate.
However, since capabilities of the auxiliary light source installed on the vehicle is limited, it is difficult for the auxiliary light source, etc. to illuminate the entire region that can be displayed. Generally, only a part of the region able to be displayed is illuminated. Therefore, when the surrounding environment is dark, a composite image displayed by the image display system includes a dark region not illuminated by the auxiliary light source or the lighting system for driving. The visibility of a subject image of an object is extremely poor in such a dark region, compared to a subject image of an object in a region illuminated. When such a subject image having poor visibility is displayed on the display, a driver who should concentrate on driving the vehicle may gaze at the screen of the display to check the subject image.